did you get to the bottom of this? - sounds like I have the same problem.
I have been running the same setup since new, approx 1.5 years old.
In the last 6 months, intermittently my PC would not wake up after going to sleep. I would have to turn power off at PSU, wait a while then turn back on. The problem became more regular and now it wont boot.
When I power on, fans turn on, lights on mobo, ram and gpu and cpu cooler come on, but no beeps, no display on monitor and no lights on keyboard or mouse. so i cant even get in to the bios.
I have removed what components I can but dont have spare to swap in and out. I have changed ram configurations around to no avail.
Spec is
Intel i7-5820K 3.30GHz (Haswell-E) Socket LGA2011-V3 Processor - Retail (BX80648I75820K)
Avexir Core White Series 32GB (4x8GB) DDR4 PC4-19200C16 2400MHz Quad Channel Kit (AVD4UZ124001608G-4
Gigabyte GeForce GTX 980Ti G1 Gaming 6144MB GDDR5 PCI-Express Graphics Card
Samsung 500GB 850 EVO SSD 2.5" SATA 6Gbps 32 Layer 3D V-NAND Solid State Drive (MZ-75E500B/EU)
NZXT H440 New 2015 Edition Case - White & Black
EVGA SuperNova G2 750W '80 Plus Gold' Modular Power Supply
Corsair Hydro H110i GT 280mm Extreme Performance Liquid CPU Cooler (CW-9060019-WW)
MSI X99A SLI Krait Edition Intel X99 (Socket 2011) DDR4 ATX Motherboard
MB-300-MS
Any ideas?